The VAV terminal unit is fitted with a differential pressure sensor for measuring the volume flow rate.

The control components (attachments) include a differential pressure transducer that transforms the differential pressure (effective pressure) into an electric signal, a controller, and an actuator; the control functions can be achieved with an Easy controller, with a Compact controller, or with individual components (Universal or LABCONTROL).

For most applications, the setpoint value comes from a room temperature controller.

The controller compares the actual value with the setpoint value and alters the control signal of the actuator if there is a difference between the two values.

An integral attenuator reduces the noise that is created by the restriction of the airflow.

The airflow velocity at the room end is, due to the larger rectangular cross section, about half the velocity in the circular duct.

Volume flow rate ranges

The minimum differential pressure of VAV terminal units is an important factor in designing the ductwork and in rating the fan including speed control.

Sufficient duct pressure must be ensured for all operating conditions and for all control units. The measurement points for fan speed control must be selected accordingly.

The volume flow rates given for VAV terminal units depend on the nominal size and on the control component (attachment) that is installed. The table gives the minimum and maximum values for a VAV terminal unit. Some control components may only have a limited volume flow rate range. This applies in particular to control components with a static differential pressure transducer. For volume flow rate ranges for all control components refer to our Easy Product Finder design programme.

Quick sizing tables provide a good overview of the room sound pressure levels that can be expected. Approximate intermediate values can be interpolated. Precise intermediate values and spectral data can be calculated with our Easy Product Finder design programme.

The first selection criteria for the nominal size are the actual volume flow rates Vmin and Vmax. The quick sizing tables are based on generally accepted attenuation levels. If the sound pressure level exceeds the required level, a larger air terminal unit and/or a silencer is required.

TVA, Sound pressure level at differential pressure 150 Pa

Nominal size

V

Air-regenerated noise

Case-radiated noise

Nominal size

V

①

②

①

③

Nominal size

V

LPA

LPA1

LPA2

LPA3

Nominal size

l/s

m³/h

dB(A)

125

15

54

18

16

15

<15

125

60

216

24

21

26

21

125

105

378

26

23

30

25

125

150

540

25

25

33

27

160

25

90

16

15

15

<15

160

100

360

28

23

24

20

160

175

630

28

23

29

24

160

250

900

23

22

32

27

200

40

144

15

<15

16

<15

200

160

576

20

17

24

20

200

280

1008

23

18

30

25

200

405

1458

26

25

32

27

250

60

216

16

<15

15

<15

250

250

900

19

16

25

20

250

430

1548

20

18

29

24

250

615

2214

27

27

33

28

315

105

378

17

15

15

<15

315

410

1476

26

21

28

23

315

720

2592

25

22

34

29

315

1030

3708

27

27

37

32

400

170

612

16

<15

17

<15

400

670

2412

18

<15

32

26

400

1175

4230

23

19

37

32

400

1680

6048

32

29

42

38

① TVA

② TVA with secondary silencer TS

③ TVA-D

Rectangular VAV terminal units for variable and constant air volume systems, suitable for extract air, available in 6 nominal sizes.

High volume flow rate control accuracy.

Ready-to-commission unit which consists of the mechanical parts and the electronic control components. Each unit contains an averaging differential pressure sensor for volume flow rate measurement, a damper blade, and an integral attenuator. Factory-assembled control components complete with wiring and tubing.

Return edges of the casing with drilled holes suitable for M10 threaded rods

TVA-D: For constructions with acoustic cladding, ducts on the room side should have cladding up to the acoustic cladding of the controller

Upstream conditions

The volume flow rate accuracy ΔV applies to a straight upstream section of the duct. Bends, junctions or a narrowing or widening of the duct cause turbulence that may affect measurement. Duct connections, e.g. branches off the main duct, must comply with EN 1505. Some installation situations require straight duct sections upstream.

Space required for commissioning and maintenance

Sufficient space must be kept clear near any attachments to allow for commissioning and maintenance. It may be necessary to provide sufficiently sized inspection access openings.

Space required

Attachments

①

②

③

Attachments

mm

VARYCONTROL

Easy controller

400

300

300

Compact controller

400

300

300

Universal controller

700

300

300

LABCONTROL

EASYLAB

900

350

400

Definition of noise

① Air-regenerated noise
② Case-radiated noise

Principal dimensions

ØD [mm]

VAV terminal units made of stainless steel: Outside diameter of the spigot

VAV terminal units made of plastic: Inside diameter of the connecting spigot

The static minimum differential pressure is equal to the pressure loss of the VAV terminal unit when the damper blade is open, caused by flow resistance (sensor tubes, damper mechanism)

If the pressure on the VAV terminal unit is too low, the setpoint volume flow rate may not be achieved, not even when the damper blade is open

Important factor in designing the ductwork and in rating the fan including speed control

Sufficient duct pressure must be ensured for all operating conditions and for all terminal units, and the measurement point or points for speed control must have been selected accordingly to achieve this

Construction

Galvanised sheet steel

Casing made of galvanised sheet steel

Parts in contact with the airflow as described for the product type

External parts, e.g. mounting brackets or covers, are usually made of galvanised sheet steel

Your message is send and will be processed shortly.Our department for Service-Requests will contact you asap.For general question regarding products or services you can also call:Tel.: +44 (0)1842 754545 | Fax: +44 (0)1842 763051

Your message is send and will be processed shortly.Our department for Service-Requests will contact you asap.For general question regarding products or services you can also call:Tel.: +44 (0)1842 754545 | Fax: +44 (0)1842 763051